The present invention is related to a gas chromatographic technique involving a gas chromatograph and a utilizing it for separation by gas chromatography and, particular, providing an improvement which achieves flows the sample applicator and in the separation column that are substantially the same in the different states in which the chromatograph is operated so as to enable control based on peak detection as well as under time control.
As disclosed in a company brochure of Siemens Aktiengesellschaft "Mehrdimensionale Chromatographie: SICHROMAT 2, der GC mit Doppelofen" (Multidimensional chromatography: SICHROMAT 2, the GC with a double oven), Order No. Al9l00-E687-A2-V1, a gas chromatograph incorporates a complicated branch piece. This component contains a long capillary, involves three different switching states, and requires two auxiliary gas flows regulated in different ways and exhibiting a differential pressure. In addition, although a monitoring detector is used, it is fed in only one of the three switching states and, thus, does not receive the entire chromatogram. Consequently, the chromatograph can only be switched based on time control, but not according to peak detection. Also, different flow conditions arise in the pre-column and the main column upon switching from one state to another. Such different flow conditions lead to an alteration of the retention times, thereby making adjustment of the time control difficult and time consuming. Moreover, intermediate cutting out can be achieved only at additional expense.